The use of longitudinally reciprocating pumps to raise fluid from a well to the surface is of long standing and generally well known in the prior art. It is typical for a well from which fluid, such as water or crude oil, is to produced to be completed with a cylindrical casing extending from the surface downward to a fluid-containing zone from which fluid is to be drawn. The casing defines the well bore and is typically perforated at the production zone to allow fluid to flow into the casing. Pumps known in the prior art typically include an elongate string of production tubing extending down the casing, with a pump body at the lower end of the tubing, typically activated by an elongate string of rods extending through the interior of the tubing. A reciprocating pumping action is utilized to lift fluid from the pump body up the production tubing upon each upstroke of the apparatus. While effective in the sense of moving fluid up the production tubing to the surface, there are significant disadvantages and inefficiencies associated with pumps previously known in the art.
In many instances, the fluid to be produced is located a substantial distance below the surface, so that the weight of the activation rods, typically referred to as "sucker rods," and pump is also substantial. Since prior art pumps move fluid toward the surface by lifting the fluid on the upstroke of the pump apparatus, it is necessary to lift not only the weight of the column of fluid, but also the weight of the sucker rods and reciprocating pump components on each production stroke. With prior art pump designs no fluid production occurs on the downstroke, which serves only to lower the apparatus for another upstroke. The lifting of the weight of the reciprocating production apparatus on each production stroke is inefficient and directly wasteful of energy, since energy associated with downward movement of the pumping apparatus on each downstroke is not utilized for any productive purpose.
There remains a need for a pumping apparatus for production of fluid from a well that efficiently utilizes the energy available for fluid production to the surface. Accordingly, it is among the objects of the invention to provide a pumping apparatus without the inefficiencies and disadvantages of the prior art. It is also among the objects of the invention to provide a pumping apparatus that utilizes the energy added to the pumping apparatus during upstroke to produce fluid on the downstroke. It is further among the objects of the invention to utilize the weight of the sucker rods and reciprocating pump apparatus and its movement in response to gravity as a source of pumping energy. It is additionally among the objects of the invention to provide a self-adjusting sealing means between reciprocating pump components and stationary pump components to automatically compensate for wear.